This invention relates to toggle actuated, snap-action switches having two-stage operating characteristics suitable for opening and closing electrical contacts. Over-toggle drive spring members are provided to initiate the force required for operating the contacts by means of an operating member. The operating member serves to actuate additional over-toggle contact operating mechanisms and thereby provide increased contact pressure.
Heretofore, many snap-action toggle operated switches were of a construction that permitted "teasing" of the contacts, especially when the switch mechanism was manually operated. In addition, although previous constructions were suitable for use in both manual and mechanical applications, they were principally designed for mechanical or cam operated applications, such as those used in limit switches having specially designed levers with cam followers rotatably attached to the outer ends of the levers.
The present switch module takes the general form of the module illustrated and claimed in U.S. Pat. No. 3,769,474 granted to Deubel et al, and assigned to the assignee of the present invention. The Deubel et al patent disclosed a switch module which provided an advancement in the art which served a needed purpose of closing and opening electrical contacts in response to slowly advancing actuation, as in thermostatic controls or the like. The main objective of the invention, as set forth in the patent, was to minimize the problems of prior switches which tended to hover for considerable periods in close vicinity of the snap-over point without positively forcing the contacts into engagement or disengagement. Such hovering conditions often led to detrimental heating and welding of contact. The construction of U.S. Pat. No. 3,769,474 provided a relatively short stroke of operation and tripped within close limits, requiring additional precision in calculating the trip points.
In the present switch construction, the mechanism is designed for both mechanical and manual application, and provides contact spinners which are both electrically and mechanically isolated from one another. The switch mechanism is rugged and has a relatively long operating stroke. In addition, there is a positive contact break feature which enhances the ability to disengage the contacts should an external circuit condition tend to cause them to overheat or weld. The construction further permits actuation of the contacts under positive force by the operator in either direction, even in a remote case where the drive springs do not provide sufficient force because of breakage, accidental removal, etc. Thus, in the case of a pushbutton, the operator may either be manually actuated to directly open the contacts or disengage the contacts, and thereby override the toggle action. In other words, a relatively large force exerted against the operator may be transmitted directly to the contacts, as in the case of pushbuttons, foot switches or limit switches placed in relatively rugged operating environments.